I have a really awful ex (fortunately no kids) and he keeps doing stuff to attract my attention, which makes it worse. After cheating on me during lockdown when I couldn't see him initially (live 2 hours away), he moved in a different, homeless woman. I found out about both and ditched him and gave him some choice words and blocked him. He then married the woman 6 months later and converted lets say to a religion sometimes associated with fundamentalism. 6 months after he got married, he turned up at my doorstep with a sob story/pity play and I told him to get lost. I wasn't actually aware that he had got married at this point. A friend told me. I am sure he thinks I'm being really unreasonable for turning him down and I sub-consciously feel he is very angry at me about it!
He then contacted a local newspaper to run a story about how he met his new wife, calling her his soulmate, etc and they ran an article about it and his local business (I can't say what kind of business it is but it would make sense if I did). I mean, who does that fgs? It went into loads of detail too and it was clear from the dates that he had cheated with us both for at least 6 months. He was always really secretive and had spun me a line for years about how he had to live alone but might one day be able to progress our relationship, and I was stupidly besotted with him until I found out about the cheating and saw the light.
I don't even feel upset any more and am conscious to react but I sort of watch from a distance, out of concern for the woman he has married, barely knows and who comes from a completely different culture. His previous girlfriend to me committed suicide a few months after we got together, but I didn't know about it and only worked out the dates later after searching online.
These people are damaging and I'm not convinced that all the trite advice to ignore, block, seek therapy, etc are always good advice. That just normalises their behaviour as something standard in the world of dating when in reality you are probably dealing with someone with a serious personality disorder. What you need to do is to learn to restore boundaries that have been eroded by their insidious behaviour or which might have been weak in the first place, and to avoid making it all about you running around after them to correct your behaviour, which there was nothing wrong with in the first place. And staying the heck away from them! In my case, it was actually quite a bad idea to block him on all social media because I was unaware he had got married when he turned up at my house, and if it had been sooner and I hadn't gone off him so much, I might have been tempted to let him in and got upset all over again.
I do miss my innocence though and wish I'd never met him.